1. Field of Invention
This invention relates to closing seams in joining the ends of wide heavy fabrics whose edges are provided with complementary arrays of separable intermeshing loops.
It is specially applicable to joining the ends of woven synthetic dryer fabrics or felts, as used in the dryer section of paper making machines and will be described specifically in this context. These fabrics are usually woven of natural or synthetic fibers bulked or layered to produce a heavy woven structure which can be for example from about 1/32 to about 1/8 of an inch thick. They are supplied in various widths from about 5 feet to about 30 feet depending on the width of the paper machine, and in length from about 40 feet to about 350 feet.
Some dryer fabrics may be woven endless. However, with fabrics more than 120 feet or so in length, endless weaving is not practical. It is more common to weave the felt as a long wide flat single piece and then join the ends to make and endless belt. The ends are each provided with an array of clipper-type loops or with an array of loops of either plastic or metal sewn in or otherwise attached. In making the joints, the ends of the cloth are forced together so that the array of loops of one end is intermeshed with the array of loops of the other. All the loops are thus brought into register so that they form an elongated tubular passage into and through which a hinge pin or pintle wire is inserted to form a hinge-type joint.
The structure of the dryer felt makes it relatively pliable in the machine direction and relatively rigid in the cross machine direction. Because the felt is heavy, wide and unwieldy and there is tension on it as it is installed on the machine it is hard to pull the two ends of the fabric together and hold their respective arrays of loops in accurate register while the pintle wire is inserted. Considerable force and dexterity is required. The problem is specially difficult with wide heavy felt.
In the course of aligning and intermeshing the loops, once a start has been made at one side of the felt, it is generally quite easy to start inserting the pintle wire. However, once the pintle wire has been inserted for a certain distance, say three or four feet, such resistance is encountered that further insertion becomes difficult or impossible. The weight of the two ends of the fabric tends to force them apart and the strain on the fabric, in pulling the ends together distorts the loops making perfect alignment difficult. At the same time, the loops through which the wire has already been inserted are pulled against it and the resulting friction resists its further insertion.
2. Description of Prior Art
Various ways have been tried to make it easier to insert the pintle wire. One way has been to rotate it as it is being inserted, for example, with an electric drill. Another is first to insert a relatively small diameter pilot wire of hard tempered steel and then use the pilot wire to pull the larger more flexible pintle wire through the socket. Still another way, if the wire is of a structure that may be pushed through the loops without too much friction or distortion, is simply to provide it with a point. Another rather crude method is to bring the ends of the fabric together intermeshing their loops and temporarily nailing the ends to a board until the pintle wire has been inserted. This is only effective with narrow dryer felts and, in any case, tends to damage the cloth.
All these methods are awkward, and, since they are time consuming, they result in considerable down time while the entire machine is shut down for installation of the dryer felt.